Weston C, Poyner D, Patel V, Dowell S, Ladds G
Division of Biomedical Cell Biology, Warwick Medical School, University of Warwick, Coventry, UK.
Br J Pharmacol. 2014 Aug;171(15):3651-65. doi: 10.1111/bph.12716.
The glucagon-like peptide 1 (GLP-1) receptor performs an important role in glycaemic control, stimulating the release of insulin. It is an attractive target for treating type 2 diabetes. Recently, several reports of adverse side effects following prolonged use of GLP-1 receptor therapies have emerged: most likely due to an incomplete understanding of signalling complexities.
We describe the expression of the GLP-1 receptor in a panel of modified yeast strains that couple receptor activation to cell growth via single Gα/yeast chimeras. This assay enables the study of individual ligand-receptor G protein coupling preferences and the quantification of the effect of GLP-1 receptor ligands on G protein selectivity.
The GLP-1 receptor functionally coupled to the chimeras representing the human Gαs, Gαi and Gαq subunits. Calculation of the dissociation constant for a receptor antagonist, exendin-3 revealed no significant difference between the two systems. We obtained previously unobserved differences in G protein signalling bias for clinically relevant therapeutic agents, liraglutide and exenatide; the latter displaying significant bias for the Gαi pathway. We extended the use of the system to investigate small-molecule allosteric compounds and the closely related glucagon receptor.
These results provide a better understanding of the molecular events involved in GLP-1 receptor pleiotropic signalling and establish the yeast platform as a robust tool to screen for more selective, efficacious compounds acting at this important class of receptors in the future.
胰高血糖素样肽1（GLP-1）受体在血糖控制中发挥着重要作用，可刺激胰岛素释放。它是治疗2型糖尿病的一个有吸引力的靶点。最近，有几篇关于长期使用GLP-1受体疗法后出现不良副作用的报道：很可能是由于对信号复杂性的理解不完整。
我们描述了GLP-1受体在一组经修饰的酵母菌株中的表达情况，这些菌株通过单个Gα/酵母嵌合体将受体激活与细胞生长联系起来。该检测方法能够研究单个配体-受体G蛋白偶联偏好，并对GLP-1受体配体对G蛋白选择性的影响进行定量分析。
GLP-1受体在功能上与代表人类Gαs、Gαi和Gαq亚基的嵌合体偶联。计算一种受体拮抗剂艾塞那肽-3的解离常数，结果显示两个系统之间没有显著差异。我们发现了临床上相关治疗药物利拉鲁肽和艾塞那肽在G蛋白信号偏向性方面存在此前未观察到的差异；后者对Gαi途径表现出显著的偏向性。我们扩展了该系统的用途，以研究小分子变构化合物以及密切相关的胰高血糖素受体。
这些结果有助于更好地理解GLP-1受体多效性信号传导所涉及的分子事件，并将酵母平台确立为一种强大的工具，以便未来筛选作用于这类重要受体的更具选择性、更有效的化合物。
